Peel and cut into pieces and boil the sweet potato. Boil the garbanzo beans until the skins come off. Remove the skins, drain, and combine all ingredients in a food processor. Blend until smooth adding small amounts of oil and water until desired consistency is achieved (this recipe usually requires more liquid, as the potato will absorb a lot of liquid.) Add salt to taste and more lemon, if needed. Enjoy with pita chips!